NATUKUNDA Temp gradient drilling and measurements at ...

TEMPERATURE GRADIENT TEMPERATURE GRADIENT DRILLING AND DRILLING AND

MEASUREMENTS AT KIBIRO MEASUREMENTS AT KIBIRO AND KATWE GEOTHERMAL AND KATWE GEOTHERMAL

FIELDSFIELDS

ARGeoC2, Entebbe, UgandaARGeoC2, Entebbe, Uganda25th November 2008

James Francis Natukunda James Francis Natukunda (DGSM), Gestur Gislason (Reyjavik (DGSM), Gestur Gislason (Reyjavik Geothermal) and Knutur Arnason (ISOR)Geothermal) and Knutur Arnason (ISOR)

9th November 20089th November 2008 22

ContentsContents1.1. Kibiro geothermal fieldKibiro geothermal field

-- Background Background -- geology & geophysicsgeology & geophysics-- Temperature gradient measurements Temperature gradient measurements -- ConclusionsConclusions-- RecommendationsRecommendations

2. Katwe geothermal field2. Katwe geothermal field-- BackgroundBackground-- Geophysical surveysGeophysical surveys-- Temperature gradient measurementsTemperature gradient measurements-- ConclusionsConclusions-- RecommendationsRecommendations


African Rift SystemAfrican Rift System


Ugandan geothermal areasUgandan geothermal areas


Kibiro geothermal Kibiro geothermal fieldfield


Background Background -- Kibiro geologyKibiro geology

West of escarpment West of escarpment --sediments sediments -- 44--5 km 5 km thickthickEast of escarpment East of escarpment –– Block faulted Block faulted granites & gneissesgranites & gneissesManifestations: hot Manifestations: hot springs, sulphur springs, sulphur deposits on the deposits on the escarpmentescarpment


Background Background -- Geophysical SurveysGeophysical Surveys

Kigorobya

Kibiro

Gravity high

Kigorobya

Kibiro

Gravity high

Low resisitivity anomaly in crystalline Low resisitivity anomaly in crystalline basement; conductive alteration minerals basement; conductive alteration minerals in fractures suggested.in fractures suggested.

Gravity high coincides with low Gravity high coincides with low resisitivity;resisitivity;-- a deep high density a deep high density intrusive suggested.intrusive suggested.

TEMTEM GravityGravity


KIBH 116°C/km

KIBH 216°C/km

KIBH 316°C/km

KIBH 531°C/km

KIBH 4 27°C/km

KIBH 616°C/km

TemperaturTemperature Gradient e Gradient --KibiroKibiro

6 gradient wells 6 gradient wells were drilled in were drilled in crystalline crystalline basementbasement


The latest The latest temperature temperature

measurements in measurements in all the holes in the all the holes in the

Kibiro areaKibiro area

Kibiro Kibiro --Temperature Gradient Temperature Gradient measurementsmeasurements


Kibiro Kibiro -- borehole geologyborehole geology


No evidence of hydrothermal alteration in No evidence of hydrothermal alteration in boreholesboreholesThe gradient temperature drilling has shown that The gradient temperature drilling has shown that the lowthe low--resistivity anomalies in the basement resistivity anomalies in the basement rocks are not caused by existing heat anomalyrocks are not caused by existing heat anomalyThe apparent epidote and sulfide appear to have The apparent epidote and sulfide appear to have been formed at much earlier time rather than been formed at much earlier time rather than geothermal activity at the current erosional levelgeothermal activity at the current erosional levelThe anomalies could be caused by epithermal The anomalies could be caused by epithermal ore depositsore deposits

Kibiro Kibiro -- ConclusionsConclusions


Kibiro Kibiro -- RecommendationsRecommendations

Carry out MT survey around Escarpment to Carry out MT survey around Escarpment to look the deeper structures of the Rift to locate look the deeper structures of the Rift to locate deeper drilling sitesdeeper drilling sites


Katwe geothermal Katwe geothermal fieldfield


Background Background -- GeologyGeology

Explosion craters, Explosion craters, pyroclastic lava pyroclastic lava blocks, tuffs & fragts blocks, tuffs & fragts of granites and of granites and gneisses deposited gneisses deposited on Pleistocene sedts.on Pleistocene sedts.Lava flows in L. Lava flows in L. Kitagata and Kitagata and Kyemengo cratersKyemengo cratersTravertine in L. Katwe Travertine in L. Katwe & near L. Kikorongo& near L. Kikorongo


Background Background -- GeophysicsGeophysicsGeophysical Geophysical surveys (TEM & surveys (TEM & gravity) delineated gravity) delineated anomalous areas anomalous areas for drillingfor drilling

Katwe: Resisitivity & gravity results


Geology Geology ––Evidence of Evidence of permeability permeability & heat & heat source source Drill sites and Drill sites and accidental accidental fragment fragment mapmap

Background Background -- GeologyGeology

Temperature Gradient Temperature Gradient measurementsmeasurements


Temperature gradient Temperature gradient

6 gradient wells were 6 gradient wells were drilled; 5 in drilled; 5 in volcanic/sediment volcanic/sediment formation & 1 in crystalline formation & 1 in crystalline basement (control)basement (control)

Samples were taken at 2 Samples were taken at 2 m interval, totaling 900 & m interval, totaling 900 & analyzed using binocular analyzed using binocular stereomicroscope at stereomicroscope at Iceland GeoSurveyIceland GeoSurvey


Temp. Temp. Gradient Gradient Measurement Measurement at KTWH 4at KTWH 4

Results: Katwe & Kibiro contd.Results: Katwe & Kibiro contd.


36°C/km

36°C/km

28°C/km

13°C/km

30°C/km

34°C/km

Results: Katwe & Kibiro contd.Results: Katwe & Kibiro contd.


Indication of geothermal Indication of geothermal activity, i.e. fracturing, activity, i.e. fracturing, veining, void fillings were veining, void fillings were not seen in samples not seen in samples ––indication of absence of indication of absence of shallow reservoir & shallow reservoir & suggesting deep seated suggesting deep seated reservoir reservoir

Borehole geologyBorehole geology


ConclusionsConclusionsThe geothermal gradient drilling operation The geothermal gradient drilling operation have not shown anomalous temperature have not shown anomalous temperature at shallow depth in Katweat shallow depth in KatweWith the current knowledge the With the current knowledge the geothermal potental of the Katwe geothermal potental of the Katwe ––Kikorongo field cannot be be confirmedKikorongo field cannot be be confirmedCarryout magnetotellurics (MT) surveys, Carryout magnetotellurics (MT) surveys, to probe deeper and identify the heat to probe deeper and identify the heat source in Katwe and Kibiro areas.source in Katwe and Kibiro areas.


Thank youThank you

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